The clinical profiles of several developmental disorders, including autism spectrum disorders (ASD), involve varying degrees of comorbid language impairment (LI). Clinical diagnosis of LI, however, does not itself identify the associated underlying neuronal deficit(s), which may occur at the level of perception, processing, and/or cognition, given the observed heterogeneity of LI. Current understanding of how a deficit at each or any of these levels might relate to LI is not sufficiently sophisticated to distinguish neuronally-based subtypes of LI. Such classification may, on the one hand, reproduce existing clinical categories, or, on the other hand, cut across clinical diagnoses and instead group together language impaired individuals by the nature of their underlying neuronal deficit. Successful implementation of the proposed research program will represent progress towards delineating subtypes of LI identified via parametric investigation of evoked neuromagnetic activity during speech perception, processing, and cognition in young clinical populations vs. typically developing peers. Specifically a population of children with autism spectrum disorders (both with and without concomitant LI) will be investigated to find neuronal characteristics associated with both autism per se and LI per se, as well as in combination. As such, it is the goal of this proposal to define electrophysiological signatures, or endophenotypes, associated with the neural correlates of LI in ASD to address both the heterogeneity of the behavioral impairment across the spectrum within the diagnosis of ASD (the "heterogeneity" problem) and the apparent overlap in behavioral impairment between different diagnoses (the "overlap" problem).